Since we are on the topic of believable dragons, here's a wonderful anatomical chart by Todd Lockwood.

Believability has always been a large part of Todd's dragon designs. He is hoping to explore that notion further, and create a complete skeletal chart to accompany this piece.
Todd says:

"The skeletal chart might also include details of how the bones are part of the respiratory system, like an advanced form of real-world birds: some of the long, hollow bones are useful in a bird's lungs, which are not bellows like ours, with air entering and leaving through the same opening, but more like a tube in which air enters at one end and leaves at the other. The hollow interior of a dragon's bones ought to be able to utilize oxygen too. Waste nothing!"

For more amazing dragons, and info on how to purchase prints of pieces like the one above, check out Todd's website at: http://www.toddlockwood.com/